Rheostat.



mmm John W. Howell.

J. W. HOWELL. BHEOSTAT.

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APPLIOATION FILED NOV- 23. 1903.

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UNITED STATES Patented July 18, 1905.

PATENT OFFICE.

JOHN 'VV. HOWELL, NEWARK, NEW JERSEY, ASSIGNOR TO GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

RH EOSTAT.

h V SPECIFICATION fornring part of Letters Patent No. 794,983, datedJuly18, 1905,

Application filed November 23, 1908. Serial No. 182.275.

To all whom, it may concern.-

Be it known that I, JOHN W. HOWELL, a citizen of the United States,residing at Newark,

county of Essex, and State of New Jersey, have invented certain new anduseful Improvements in Rheostats, of which the following is aspecification.

This invention relates to rheostats; and its object is'to provide adevice in which both the current-carrying capacity and the resistancecan be varied as desired.

I In manyclasses of work it is necessary to varythe resistance of acircuit over a wide range. If the potential of the circuit is constant,the current varies inversely as the re- 'sistance, and if the variationisaccomplished with a rheostat similar to those'now in com- V men usethe resistance material of the rheostat I must be such that it willcarry without dangerous heating the heavy current flowing in the circuitwhen the minimum resistance is cut in. 'If the resistance med um 1s awire, it must .is therefore possible to use a smaller resistance-wire ofsuch capacity that it will carry the current without dangerous heatingonly when a comparatively heavy .resistance is cut in and to use two ormore lengths of the wire in parallel when a greater current is wanted,and as only a small section of the resistancecoil is needed when thelarger current is being used the parallel circuits may all be throughthe resistance material whichwas used in a single circuit to obtain thehigh resistance. I have therefore provided a rheostat of the slide-wiretype having resistancewire wound on a tube and two insulated rodsmounted parallel to the tube, on each of which one or any number ofcontacts bearing on the wire may be adjusted as desired. If one contactis mounted oneach rod at opposite ends of the coil, the maximumresistance is cut in and the fiow'of current in the circuit is small. Bybringing the contacts closer together the resistance is reduced and thecurrent increased until the latter approaches the current capacity ofthe wire. Beyond this point a further reduction of the resistance ismade by placing another contact on one of the rods, so as to establishtwo circuits through the coil, thus effecting the desired reduction anddoubling the current-carrying capacity. In this way more contacts may beadded to get any desired capacity and the contacts may be adjusted alongthe rods to get a delicate regulation of the resistance. It will thus beseen that an exceedingly wide range of resistance and capacityrelatively to the size of the device is obtained. My invention thereforecomprises a rheostat the current-carrying capacity of which isadjustable and in which the resistance in circuit can be regulated asdesired for any adjustment of the current-carrying capacity.

It also comprises other novel features which will be definitelyindicated in the appended claims.

1n the accompanying drawings, whieh. illustrate one embodiment of myinvention, Figure 1 is a top view of my improved rheostat. Fig. 2 is anend view, and Fig. 3 a cross-sec-- tion of the same, and Fig. 4 is adetail view of one of the contacts.

Referring to the drawings, 1 l arestand- .ards by which the rheostat. ismounted on a suitable base and which are arranged to support a metaltube 2, covered with asbestos or other suitable insulating material 3. Aresistance-wire 4c is tightly wound on the tube over the asbestoscovering 3; Mounted on the standards 1, but insulated therefrom, as

. shown, are rods 5 5, one on either side of the tube and parallelingthe tube throughout its length. Contact-carriers 6 6 (shown in detail inFig. 4:) are adapted to slide on the rods 5 5. The carriers are providedwith springmetal sides 7 7 to insure a good contact with the rods andare open at the bottom, so that they can be readily sprung on the rodsor withdrawn therefrom. A spring-contact 8 is mounted on the side ofeach carrier 6 and adapted to bear on the resistance-wire the point ofcontact with the wire being in line with the end of the carrier. Therods 5 are marked ofi" to a suitable scale to facilitate positioning thecontacts on one rod in a definite relation to those on the other.Bindingscrews 9 9 are provided on the rods 5 5 for connecting the devicein circuit. I

With the contacts arranged as shown in Fig. 1 there are two circuits ofequal resistance through the wire 4, and the current capacity of therheostat is double that of the wire. The two carriers on one rodcan beadjusted toward or away from the one onthe opposite rod to regulate theresistance in circuit, the marks on the rods enabling the operator tomake the two circuits equal in ,resistance. If the two contacts weremuch closer together, the current flowing through each path wouldapproach the capacity of the wire, and further reductions in theresistance would be made by placing other carriers on therods and movingthem into engagement with the wire at another part of the coil, therebyestablishing other paths for the current through the coil, decreasingthe resistance and increasing the current capacity of the rheostat.

What I claim as new, and desire to secure by Letters Patent of theUnited States, is

1. A rheostat having means for adjusting the current-carrying capacitythereof, and for varying the resistance in circuit for any adjustment ofthe current-carrying capacity..

2. In a rheostat, a resistance, and means for closing a singlecircuit ora plurality of par allel circuits through the resistance, and forvarying the resistance of the single circuit or one of the parallelcircuits.

3; In a rheostat, a resistance, and means for closing a single circuitor a plurality of parallel circuits through the resistance, and forvarying the resistance of the several circuits. 4. In a rheostat, aresistance, means for connecting a variable portion of said resistancein circuit, and means for establishing parallel. circuitsthrough theresistance, and

varying the resistance of one of the parallel circuits independently ofanother.

5. In a rheostat, a resistance, and ad ust- 'able contacts for closing aplurality of parallel circuits through the resistance'to obtain a highcurrent-carrying capacity, for varying the resistance oi said circuits,and i OF OPGI'P, ing any circuit to increase the resistance.

6. In a slide-wire rheostat, a resistance, and movablecontacts forclosing a circuit through the resistance and varying the amount ofresistance in circuit, for establishing parallel circuits through theresistance, and for varying the resistance of the parallel circuits.

'7. In a rheostat, the combination of a single resistance unit, and aplurality of adjustable contacts to establish a number of variableparallel paths for the currentwhereby the capacity or ohmic value of theunit may be va- 1'1G( r 8. A slide-wire rheostat having a tube,resistance thereon, two rods mounted parallel to the tube, and aplurality of contacts adjustably mounted on said rods and adapted tomake contact with the wire.

9. In a rheostat, a tube, resistance wound thereon, a plurality of rodsparallel to the tube, and a plurality of contacts adapted to be quicklyplaced on a rod in contact with the resistance-Wire and withdrawntherefrom.

10. In a rheostat, a tube, resistance wound thereon, a plurality of rodsmarked to a delinite scale mounted parallel to the tube, and a pluralityof contacts adapted to be quickly placed on a rod in contact with theresistancewire and withdrawn from the rod. v 11. in a rheostat,standards, a tube mounted thereon, resistance on the tube, two rodsmounted on the standards parallel to the tube but insulated from thestandards, said rods being marked to a definite scale, and a pluralityo1 contacts arranged to be mounted for longitudinal movement on a rod tocross-connect the rod and resistance-coil.

in witness whereof I have hereunto set my hand this-th day of November,1903.

JOHN VJ. HOWELL. Witnesses:

S. N. Wurrnnnan, JOHN lvirrouruzn, Jr.

